Possible enhancement of the superconductingTcdue to sharp Kohn-like soft phonon anomalies

Cunyuan Jiang; Enrico Beneduce; Matteo Baggioli; Chandan Setty; Alessio Zaccone

doi:10.1088/1361-648X/acbd0a

Possible enhancement of the superconductingTcdue to sharp Kohn-like soft phonon anomalies

J Phys Condens Matter. 2023 Feb 24;35(16). doi: 10.1088/1361-648X/acbd0a.

Authors

Cunyuan Jiang¹, Enrico Beneduce², Matteo Baggioli^{1

3

4}, Chandan Setty⁵, Alessio Zaccone²

Affiliations

¹ School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
² Department of Physics "A. Pontremoli", University of Milan, via Celoria 16, 20133 Milan, Italy.
³ Wilczek Quantum Center, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
⁴ Shanghai Research Center for Quantum Sciences, Shanghai 201315, People's Republic of China.
⁵ Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, TX 77005, United States of America.

PMID: 36808073
DOI: 10.1088/1361-648X/acbd0a

Abstract

Phonon softening is a ubiquitous phenomenon in condensed matter systems which is often associated with charge density wave (CDW) instabilities and anharmonicity. The interplay between phonon softening, CDW and superconductivity is a topic of intense debate. In this work, the effects of anomalous soft phonon instabilities on superconductivity are studied based on a recently developed theoretical framework that accounts for phonon damping and softening within the Migdal-Eliashberg theory. Model calculations show that the phonon softening in the form of a sharp dip in the phonon dispersion relation, either acoustic or optical (including the case of Kohn-type anomalies typically associated with CDW), can cause a manifold increase of the electron-phonon coupling constantλ. This, under certain conditions, which are consistent with the concept of optimal frequency introduced by Bergmann and Rainer, can produce a large increase of the superconducting transition temperatureTc. In summary, our results suggest the possibility of reaching high-temperature superconductivity by exploiting soft phonon anomalies restricted in momentum space.

Keywords: charge density wave; phonon softening; superconductivity.